1. Field of the Invention.
The present invention relates to a rail car with a substructure and a car body arranged thereon having a main suspension system on a fluid basis provided with at least one strut supporting the car body against the substructure, the pressure prevailing in said strut being correlated to the weight of the car body, and at least one emergency spring supporting the car body against the substructure in case of a failure of the main suspension.
2. Description of the Prior Art.
With rail cars of the type mentioned herein above, it may happen that, on entering a station, the level of the floor arranged in a car body is higher than the platform level in the station. Due to the level difference between the station and the upper edge of the floor in the car body, a step may form in the area of transition between the rail car and the station.
With rail cars intended for passenger service mainly, these steps may pose a considerable safety risk for passengers, this being the reason why level adjustment may be carried out. For this purpose, the car body is usually lowered into an active main spring arranged between the car body and the chassis by reducing the dynamic spring travel. However, the reduction of the dynamic spring travel of the active spring involves the risk that, upon failure of a level adjustment, the dynamic spring travel available does no longer suffice to ensure safe driving. Accordingly, driving is no longer possible upon failure of conventional level adjustments. To circumvent the problem just mentioned, certain known level adjustments for rail cars are provided, together with the active spring, with a passive emergency:spring that is intended to allow for sufficient suspension travel of the car body in case of a failure of the active spring.
A rail car of the type mentioned herein above is disclosed in WO 94/22702 A1 for example. The known rail car is provided with a hydraulic strut arranged between the car body and the substructure. To lower the car body, the dynamic spring travel of the active strut can be reduced by discharging oil into a spring chamber. DE 198 15 197 C1 also describes that, on a pressure drop, the car can be lowered onto an emergency spring. Like with all of the other known level adjustment systems using an emergency spring in addition to an active spring, the disadvantage of this embodiment is that the travel of the active spring is limited by the emergency spring in xe2x80x9cdownwardxe2x80x9ddirection toward the chassis so that it may happen that the car body cannot be completely lowered to the platform level of a station while passengers are getting into and out of the car for example.
When the level of the platform""s upper edge (FOK) in a station is so low that, on lowering the car body onto the FOK, there is no dynamic spring travel left, the problem arising is that, upon failure of conventional level adjustment systems, the derailment safety of the rail car is no longer provided. Furthermore, the action of lowering the car body is usually restricted by the xe2x80x9cemergency positionxe2x80x9dof the emergency spring in operation.
It is therefore an object of the invention to overcome the above mentioned disadvantages.
According to the invention, the solution to this object is achieved with a rail car of the type mentioned herein above in which at least one emergency spring is biased and maintained in normal operation position (FIG. 1, 2) by the force generated by the pressure prevailing in the strut, the emergency spring expanding from said normal operation position into an emergency operation position (FIG. 3) in which it resiliently supports the car body in case of a failure of the main suspension system.
In the invention, the emergency spring is always biased as long as the main spring is intact, thus requiring less space than a conventionally arranged emergency spring. The distance by which a strut of the main suspension system can be lowered in a station increases as a result thereof. Upon failure of the main suspension system, the emergency spring expands and supports the car body against the substructure, thus allowing to maintain safe driving operation.
In a preferred variant of the invention there is provided that the at least one emergency spring is accommodated in a housing comprised of an outer part connected to the car body or the substructure and of an inner part which is carried so as to be slidable in vertical direction within the outer part and carries the emergency spring, said two parts forming at least one pressure chamber filled with a fluid and bounded, at least in sections, in the direction of action of the emergency spring, by a projection of the outer part and by a projection of the inner part located opposite said outer part.
Furthermore, the loads between the at least one emergency spring and the strut may be coupled.
In an advantageous embodiment, the spring travel of the emergency spring can be limited by a catch; said catch can be formed by the base of the outer part of the housing.
Moreover, the emergency spring can be biased to block when in normal operation position and a load transmission can be provided between the strut and the emergency spring.
The emergency spring can be connected in parallel or in series with the main suspension system.